The diurnal variability of precipitation across the central Rockies and adjacent Great Plains

The diurnal variation of precipitation across Wyoming, Colorado, South Dakota, Nebraska and Kansas has been studied by means of a harmonic analysis of 35 years of hourly precipitation data for 334 stations, and a regional probability of precipitation analysis for grouped stations.New findings beyond previous work include: 1) a pervasive 0300 LST maximum for the precipitation category >0.25 mm that is most prominent during the cooler half of the year; 2) the transition from winter to spring (March/April) is accompanied by an increase in measureable precipitation frequency but a decrease in precipitation frequency for rainfall amounts >2.5 mm; and 3) the summer rainfall regime is made up of distinct local and mountain generated signals. The implication of these results is that: 1) the winter regime is affected by large scale circulation features; 2) dynamically significant precipitation systems,although infrequent, do affect the five state region in winter; and 3) heavy summer nocturnal precipitation systems over the eastern Plains cannot be explained solely by the eastward propagation of mountain generated systems from the previous afternoon. -from Authors